The oldest writing anyone has ever found was made by scribes in the city of Uruk in ancient Sumer, in what is now southern Iraq, around 3200 BC.

They pressed the end of a cut reed into a wet lump of clay.

The reed was cut on a slant, so every press made a small wedge-shape — the Latin word for wedge is cuneus, which gives us the name cuneiform.

It began as pictures — a picture of an ox meant 'ox' — but within a few hundred years the marks stood for sounds.

That is what makes it writing.

Over 500,000 clay cuneiform tablets have been dug up: laws, letters, receipts, love poems, the world's first written story — the Epic of Gilgamesh.

The Louvre museum in Paris has the Code of Hammurabi, an eight-foot-tall stone pillar covered in cuneiform law.

Try this: press your thumbnail sideways into a piece of clay or plasticine.

That single mark is the shape a whole civilisation wrote with for two thousand years.